Are humans responsible for the big jump to the West Coast?
Genetic analysis shows that the bat-killing fungus recently detected for the first time in western North America is similar to strains found in the eastern United States. That means there is a good chance that humans were involved in spreading the disease, according to conservation advocates who want resource managers to step up efforts to halt the spread of the fungus by restricting cave tourism.
The new study, published in the journal mSphere, has implications for resource managers battling the spread of a disease that has wiped out millions of bats in North America. It provides new clues about the origin of this strain of the Pseudogymnoascus destructans fungus, or Pd. The latest case of WNS near North Bend, Washington was about 1,300 miles from the previous westernmost detection in Nebraska.
Because Pd is also present in Eurasia, and North Bend is located near an international port, the scientists studied DNA from the Washington fungus to determine if it had roots abroad.
“Although it remains unclear how Pd reached Washington, this finding guides us to look to North America as the source,” said Jonathan Sleeman, director of the USGS National Wildlife Health Center (NWHC), where the Washington bat was confirmed Pd positive. “Now that Pd has been identified in the western U.S., it’s critical to continue working with resource managers to help conserve imperiled bat species, which are worth billions of dollars per year to North American agriculture and forestry.”
“The severity and potential ecosystem-level effects of WNS in North America make it one of the most serious wildlife diseases ever recorded,” said Daniel Lindner, a research plant pathologist with the Forest Service’s NRS and a co-author on the study. “We have made a lot of progress in understanding WNS and in monitoring its spread, but more work is needed to determine how disease impacts will vary among bat populations in eastern and western North America.”
Scientists at the Forest Service’s NRS sequenced DNA from multiple strains of Pd, including the fungus cultured from the Washington bat, to determine that it most closely matched fungal strains from eastern North America.
White-nose syndrome was first documented in New York state in 2006 and has rapidly spread westward in North America to neighboring states and into Canada. The disease has killed millions of beneficial, insect-eating bats and threatens several formerly abundant bat species with extinction.
Based on the current understanding of Pd distribution in North America, scientists cannot determine if the fungus reached Washington from the east by bat movements or through human activities. However, ongoing surveillance efforts coordinated through the multiagency WNS response effort continues to provide insights on the spread of WNS, the impacts of this disease on bat populations and the potential for population recovery.
“These results confirm that Pd is capable of movement far across North America. They do not, however, change the importance of taking precautions to reduce the risk of spread by humans,” said Jeremy Coleman, National WNS Coordinator for the U.S. Fish and Wildlife Service. “There’s much we don’t know about how Pd will affect populations of western bats, so it is critical to limit spread as much as possible until we can improve survival of susceptible bats.”